Laws which mean gay and lesbian asylum seekers can be returned to countries where they face persecution will be challenged tomorrow in the UK's highest court.

The supreme court is to start a three-day hearing of two separate cases brought by gay men – one from Cameroon and the other from Iran – who are appealing against previous court decisions that they should not be granted asylum in the UK.

One applicant, known as "T", is appealing against a tribunal decision that he could return to his native Cameroon, despite the fact that he was attacked by a mob after he was seen kissing a male partner.

The other, known as "J", was told by the tribunal that he could be expected to tolerate persecution arising from his homosexual relationship, and should behave discreetly to avoid reprisals.

The approach of the Home Office and the courts – which has relied on gay and lesbian asylum seekers hiding details of their sexuality to avoid persecution in countries where homosexuality is illegal or likely to lead to attacks – has been one of the most controversial aspects of UK asylum policy.

"[J's] right to the normal incidents of sexual identity … involves a right to associate and live openly with the partner of his choice, not having to lie repeatedly about a core aspect of his identity and, when single, openly seeking out the partner of his choice," his lawyer argued in previous appeals against the Home Office decision to refuse asylum.

Lawyers have also claimed that the approach is guilty of an assessment described by some as the Anne Frank principle.

"It would have been no defence to a claim that Anne Frank faced well-founded fear of persecution in 1942 to say that she was safe in a comfortable attic," Lord Justice Pill agreed in the court of appeal last year. "Refugee status cannot be denied by expecting a person to conceal aspects of identity or suppress behaviour the person should be allowed to express," he added.

But the court of appeal rejected previous attempts by "J" and "T" to remain in the UK, and has continued to interpret the law as sanctioning the return of asylum seekers if they could avoid attacks by acting with "discretion" which they could be reasonably expected to tolerate.

The cases, which have been joined because they raise similar issues about persecution and homosexuality, and will be heard by five supreme court justices, represent one of the most high-profile challenges to the UK's approach on asylum in recent years.

The hearing comes weeks after a new report on the treatment of lesbian and gay claims for asylum found that the refusal rate was 98%, compared with 73% for asylum claims generally.

"It seems that the Home Office are routinely refusing applications on the grounds that lesbians and gay men can go back and be "discreet" or "relocate", said Angela Mason, the patron of the UK Lesbian and Gay Immigration Group. "Decisions are being made by Home Office case owners who lack essential training on dealing with such claims … The result is that lesbian and gay asylum seekers who are already experiencing persecution may also face discrimination in our own country."

Treatment of gays and lesbians in both countries in question is severe. Punishment for homosexual acts ranges from public flogging to execution in Iran, and, Amnesty has said that homophobia is "endemic" in Cameroon. Sentences for homosexuality range from six months to five years.

The Home Office said it takes the sexuality of asylum seekers into account, and that each application is decided on its own merits. It is contesting the case.